Re: [PATCH vhost 3/7] vdpa/mlx5: Allow modifying multiple vq fields in one modify command

Dragos Tatulea
2023-12-01T15:26:48Z

On 12/01, Eugenio Perez Martin wrote:
> On Fri, Dec 1, 2023 at 11:49 AM Dragos Tatulea <dtatulea@nvidia.com> wrote:
> >
> > Add a bitmask variable that tracks hw vq field changes that
> > are supposed to be modified on next hw vq change command.
> >
> > This will be useful to set multiple vq fields when resuming the vq.
> >
> > The state needs to remain as a parameter as it doesn't make sense to
> > make it part of the vq struct: fw_state is updated only after a
> > successful command.
> >
>
> I don't get this paragraph, "modified_fields" is a member of
> "mlx5_vdpa_virtqueue". Am I missing something?
>
I think this paragraph adds more confusion than clarification. I meant
to say that the state argument from modified_virtqueue needs to remain
there, as opposed to integrating it into the mlx5_vdpa_virtqueue struct.

>
> > Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
> > ---
> > drivers/vdpa/mlx5/net/mlx5_vnet.c | 48 +++++++++++++++++++++++++------
> > 1 file changed, 40 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > index 12ac3397f39b..d06285e46fe2 100644
> > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > @@ -120,6 +120,9 @@ struct mlx5_vdpa_virtqueue {
> > u16 avail_idx;
> > u16 used_idx;
> > int fw_state;
> > +
> > + u64 modified_fields;
> > +
> > struct msi_map map;
> >
> > /* keep last in the struct */
> > @@ -1181,7 +1184,19 @@ static bool is_valid_state_change(int oldstate, int newstate)
> > }
> > }
> >
> > -static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, int state)
> > +static bool modifiable_virtqueue_fields(struct mlx5_vdpa_virtqueue *mvq)
> > +{
> > + /* Only state is always modifiable */
> > + if (mvq->modified_fields & ~MLX5_VIRTQ_MODIFY_MASK_STATE)
> > + return mvq->fw_state == MLX5_VIRTIO_NET_Q_OBJECT_STATE_INIT ||
> > + mvq->fw_state == MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND;
> > +
> > + return true;
> > +}
> > +
> > +static int modify_virtqueue(struct mlx5_vdpa_net *ndev,
> > + struct mlx5_vdpa_virtqueue *mvq,
> > + int state)
> > {
> > int inlen = MLX5_ST_SZ_BYTES(modify_virtio_net_q_in);
> > u32 out[MLX5_ST_SZ_DW(modify_virtio_net_q_out)] = {};
> > @@ -1193,6 +1208,9 @@ static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
> > if (mvq->fw_state == MLX5_VIRTIO_NET_Q_OBJECT_NONE)
> > return 0;
> >
> > + if (!modifiable_virtqueue_fields(mvq))
> > + return -EINVAL;
> > +
>
> I'm ok with this change, but since modified_fields is (or will be) a
> bitmap tracking changes to state, addresses, mkey, etc, doesn't have
> more sense to check it like:
>
> if (modified_fields & 1<<change_1_flag)
> // perform change 1
> if (modified_fields & 1<<change_2_flag)
> // perform change 2
> if (modified_fields & 1<<change_3_flag)
> // perform change 13
> ---
>
> Instead of:
> if (!modified_fields)
> return
>
> if (modified_fields & 1<<change_1_flag)
> // perform change 1
> if (modified_fields & 1<<change_2_flag)
> // perform change 2
>
> // perform change 3, no checking, as it is the only possible value of
> modified_fields
> ---
>
> Or am I missing something?
>
modifiable_virtqueue_fields() is meant to check that the modification is
done only in the INIT or SUSPEND state of the queue. Or did I
misunderstand your question?

> The rest looks good to me.
>
Thanks for reviewing my patches Eugenio!

> > if (!is_valid_state_change(mvq->fw_state, state))
> > return -EINVAL;
> >
> > @@ -1208,17 +1226,28 @@ static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
> > MLX5_SET(general_obj_in_cmd_hdr, cmd_hdr, uid, ndev->mvdev.res.uid);
> >
> > obj_context = MLX5_ADDR_OF(modify_virtio_net_q_in, in, obj_context);
> > - MLX5_SET64(virtio_net_q_object, obj_context, modify_field_select,
> > - MLX5_VIRTQ_MODIFY_MASK_STATE);
> > - MLX5_SET(virtio_net_q_object, obj_context, state, state);
> > + if (mvq->modified_fields & MLX5_VIRTQ_MODIFY_MASK_STATE)
> > + MLX5_SET(virtio_net_q_object, obj_context, state, state);
> > +
> > + MLX5_SET64(virtio_net_q_object, obj_context, modify_field_select, mvq->modified_fields);
> > err = mlx5_cmd_exec(ndev->mvdev.mdev, in, inlen, out, sizeof(out));
> > kfree(in);
> > if (!err)
> > mvq->fw_state = state;
> >
> > + mvq->modified_fields = 0;
> > +
> > return err;
> > }
> >
> > +static int modify_virtqueue_state(struct mlx5_vdpa_net *ndev,
> > + struct mlx5_vdpa_virtqueue *mvq,
> > + unsigned int state)
> > +{
> > + mvq->modified_fields |= MLX5_VIRTQ_MODIFY_MASK_STATE;
> > + return modify_virtqueue(ndev, mvq, state);
> > +}
> > +
> > static int counter_set_alloc(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
> > {
> > u32 in[MLX5_ST_SZ_DW(create_virtio_q_counters_in)] = {};
> > @@ -1347,7 +1376,7 @@ static int setup_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
> > goto err_vq;
> >
> > if (mvq->ready) {
> > - err = modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> > + err = modify_virtqueue_state(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> > if (err) {
> > mlx5_vdpa_warn(&ndev->mvdev, "failed to modify to ready vq idx %d(%d)\n",
> > idx, err);
> > @@ -1382,7 +1411,7 @@ static void suspend_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *m
> > if (mvq->fw_state != MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY)
> > return;
> >
> > - if (modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND))
> > + if (modify_virtqueue_state(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND))
> > mlx5_vdpa_warn(&ndev->mvdev, "modify to suspend failed\n");
> >
> > if (query_virtqueue(ndev, mvq, &attr)) {
> > @@ -1407,6 +1436,7 @@ static void teardown_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *
> > return;
> >
> > suspend_vq(ndev, mvq);
> > + mvq->modified_fields = 0;
> > destroy_virtqueue(ndev, mvq);
> > dealloc_vector(ndev, mvq);
> > counter_set_dealloc(ndev, mvq);
> > @@ -2207,7 +2237,7 @@ static void mlx5_vdpa_set_vq_ready(struct vdpa_device *vdev, u16 idx, bool ready
> > if (!ready) {
> > suspend_vq(ndev, mvq);
> > } else {
> > - err = modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> > + err = modify_virtqueue_state(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
> > if (err) {
> > mlx5_vdpa_warn(mvdev, "modify VQ %d to ready failed (%d)\n", idx, err);
> > ready = false;
> > @@ -2804,8 +2834,10 @@ static void clear_vqs_ready(struct mlx5_vdpa_net *ndev)
> > {
> > int i;
> >
> > - for (i = 0; i < ndev->mvdev.max_vqs; i++)
> > + for (i = 0; i < ndev->mvdev.max_vqs; i++) {
> > ndev->vqs[i].ready = false;
> > + ndev->vqs[i].modified_fields = 0;
> > + }
> >
> > ndev->mvdev.cvq.ready = false;
> > }
> > --
> > 2.42.0
> >
>